Production of long-chain tertiary amines



Patented Jan. 2, i945 areas b raonuc'r'rouormouo-cnamraa'rmar ames JamesEhltirbyrwilmington, DeL, assignor to :E. L du Pont de Nemours 8:Company, Wilmington, D'eL, a corporation-of Delaware No nmvm.Application July so, 1941,

l Serial No. 404.617

6 Claims. (oi. zoo-sea) i 1: relatesitothe production of amine an orcularlyit relatestoaprocroductionfof long-chain tertiary caily, thisinvention relates ring iong chain alkyl N-naturaljsou'rcesihave'for-many years been recogriiz'jedas valuable"intermediates for the synthesis offtextile Compounds containing rromgizgtpia .car

ain aliphatic l compounds derived from a his have been found to varietyf productsproduced from amides, esters,

in thisrange are how commercially available for use jas,.textil'ereagents." "More recently, longmout wash amm d importance, not only asintermediates for the manufacture of textile treating agents, but'formany other uses. Among textile chemicals prepareditrom amines, thosederived from long-chain tertiary amines have show"outstandingiyflattractive properties from the. inn ierfcial poin erview, but unfortunately, development alpngthesejlines has been hamperedseriously 'by thellack ofeconomically sound and practicable 1 methods.for thesynthesis of suitable tertiary. jhas! been proposed in theliterature to prepare'long-chain alkyl N -dimethyl amines byQreactiiiglQng-Chain allwl halides or alcohols with. dimethyflamine, bymethylatins lougichainj amines with methanol in the presence ofmineral-acid catalysts, and by reducing ;l9n85chaincarboxylic amides.All of these proposed. processes; arecharacterized by a deficiency inyield performance, by the formation of diflicultly separable mixtures ofproducts, and by excessive costs for, manufacturing N-dimethyl longchain, aliryl on, a practical commercialise-ale, l o

Thisinve'ntion has as an objectto develop a process for the productionof? long-chain tertiary amines. Another obiect is to provide a processfor the: production or} long -chain N-dimethyl amines. Still anotherobject. is to provide a smooth and low cost process for the productionof long chain tertiary high yields. Other; objects be apparent, from thefollowihgdescriptionof; theinventlom. l

biectsareac plishedbythe following invention, which comprises reducing,a mixa or ms ehv a n S d from thewlassqc m ti s-fi l nwhai P me andlong- -chain at a temperature between about 251;, about, 10020. The ream: medium i mom a the embodiments of this invention, the synthesis ofN-dimethyl long-chain alkyl amines is accomplished by treating mixturesof 12 to 18 carbon primary amines and formaldehyde in molecular ratiosof less than 1:2 with formic acid at temperatures between about 25 C.and about 100 C. Long-chain alkyi aminesare converted to thecorresponding N-dimethyl amines by reduction possess especialiitilityjiri this field. and a wide with formic acid according to thefollowing procedure. One mol of long-chain amine is charged in asuitable reaction vessel equipped with an emcient agitator, andapproximately five mole of formic acid (90% aqueous solution) is addedslowly at a rate insuiiicient to bring about a rise in temperature aboveabout C. The resulting solution is cooled to approximately roomtemperature and about 2.2 mols of formaldehyde (37% formalin) addedwithout especial precautions. The mixture is then slowly heated withstirring to a temperature of approximately 35 to 38 C. to initiate theevolution of carbon dioxide, The reaction is slightly exothermic andproceeds without further application of heat for a period of Ito 2 hoursduring which time approximately 60% of the theoretical quantity ofcarbon dioxide is evolved. At this stage of the reaction, the evolutionof gas is accompanied by severe foaming and extreme care must beexercised in adjusting the temperature to avoid loss of product.Subsequently, the temperature of.

Example I Ninety-five parts of commercial formic acid was placed in areaction vessel provided with an efllcient agitator and cooled to about10 C. in an ice bath. One hundred parts of technical stearyl aminecontaining approximately equal parts of n-hexadecyl and n-octadecylamines was melted and added slowly to the formic acid to produce a thickslurry of the corresponding salts. After stirring for a brief period,the reaction mixture was allowed to warm up to room temperature and 71parts of formalin solution containing 37% by weight of formaldehydeadded rapidly. At room temperature evidence of reaction was slight, buton heating slowly to about 35 0., evolution of carbon dioxide began at asteady rate. This was accompanied by the formation of a thick head ofviscous ioam onthe surface of the reaction mixture, audit was necessaryto exercise extreme care in adjusting the temperature and trample III1500 parts of crude, technical stearylamine containing approximately 90%or n-hexadecyl and rate of stirring to avoid losing the product. By 1operating between about 40 and about 43 (2..

approximately 60% of the theoretical quantity of 1 carbon dioxide wasevolved during about 2 hours.

by the quantity of gas evolved, the mixture was brought to the boilingpoint (94 C.) and the re-' action completed by refluxing for a period of1 t 1.5 hours. The resulting product consisted of a thick syrupy liquid,which was transferred to an evaporation pan, treated with'a slightexcess of concentrated hydrochloric acid to decompose amine-formic acidsalts, and evaporated to a thick paste, to remove unreacted formaldehydeand formic acid. The-residue was then taken up in hot water and treatedwith an excess of caustic alkali solution. The liberated amines wereseparated by extraction with benzene. Fractional distillation of thebenzene extract gave 41.5 parts of N-dimethylhexadeeylamine, B. P. 175'/6 mm.; 14.8 parts of mixture of N-dimethylhexadecyl andN-dimethyloctadecyl amines; 30.2 parts of N-dimethyloctadecylamine, B.P. 194 C. at 6 mm.; and 10.8 parts of high boiling residue. The

combined yield of N-dimethyl long-chain alkyl amines was about 80% oftheory.

Example 11 Six hundred forty parts of 90% formic acid solution was addedslowly with stirring to 465 arts of pure n-dodecylamine. Theneutralization was accompanied by the evolution of considerable heat,and the rate of addition was controlled to avoid exceeding a temperatureof about 65 C. The resulting mixture was cooled to below 30 C. and 446parts of 37% formalin solution added rapidly. Only a slight thermalefiect was noted and the mixture'was heated cautiously to approximately35C. At this temperature an exothermic reaction set in, and theevolution of carbon dioxid began at a steady rate. The reactioncontinued without iurther application of heat for about 1 to 1.5 hours,during which time the temperature remained at 42 to 44 C. and the amountof gas given off was 60% to 65% of theory. During this period foamingwas severe, but the tenacity of the foam was somewhat less than in thecase of the higher members of the series. The reaction was completed byboiling under reflux for an additional period of about 3 hours until thevolution of carbon dioxide had essentially stopped. The

syrupy product was treated with a slight excess of concentratedhydrochloric acid, evaporated overnight to eliminate'unreacted formicacid and formaldehyde, and finally made strongly alkaline to liberatethe free amines. The oily prodnot was separated from the aqueoussolution by extracting thoroughly with successive portions of benzene.Fractional distillation of the combined benzene extracts gave 460- partsof pure N-dimethyldodecylamine, B. P. 121 to 122' C. at mm. Themolecular yield was 86.5% of-theory.

n-octadecylamines and 7% to 10% of the corresponding secondary amineswere treated with 1425 parts, of 90% formic Q1d8-933 parts of 37%formalinaccordingito the procedure of Example II. On working up theproduct by vacuum fractional distillation there were obtained 59.7parts. of lower N-dimethyl alkyl amines, B. P. 105 to 173 C. at 5 mmi;440 parts of N-dimethyl cetylamine, B. P. 173 to 175 C. at 5 mm.: 66.6parts of an intermediate fraction, B. P. 175 to 4190" c. at? 5 mm.;538.2 parts of N-dimethyloctadecylamine,B. P. 190" C. at 5 mm., and 338h parts oif high boiling residual products.

Example 1V One hundred parts of 7-aminoheptadecane was charged into asuitable corrosion-resistant reaction vessel equipped with an emcientagitator.

' with vigorous stirring, 100 parts of 90% formic acid was added to theamine'at a rate adiusted to avoid an exothermic temperature rise aboveC. The resulting mixture was cooled to room temperature and parts of 37%formalin solution added. On warming to about 35 to 38' C. reductionbegan as evidenced by the evolution of carbon dioxide. The temperatureof the mixture was raised gradually during a period of about 3 hours,care being taken to avoid overheating and excessive foaming. Thereaction was completed by boiling the solution under reilux for onehour. 'On'w'orking up the product according to the procedure of Example"I there was obtained 100.1 parts of 7-dimethylaminoheptadecane, B. P.164 to' 166 Cxat 4 mm. The molecularyi'eld was 90.2%.

Example V Three hundred sixty grams of dodecylamine was placed in a 12liter flask fitted with a stirrer and thermometer. With vigorousstirring oi the amine paraformaldehyde was gradually added over a periodof V hour. During this addition the temperature rose from about 28toabout 69 C. While controlling the temperature between 43 and 67 C.,257 grams of formic acid-was added dropwise over a period ofabout l-hourand 55 minutes. Ether was addedto the fla'sk in such quantities as tokeep the reaction-from foaming so violently due to the evolution ofcarbon dioxide that the reaction mixture would be lost. After all theformic acid had been addedthe reaction mixture was heated on a steambath for 2 hours and 10 minutes and then allowed to remain at roomtemperature for 16 hours. The reaction mixture was then diluted withwater, treated with 280 grams of sodium hydroxide and extracted withether. The resulting product was then dried over potassium hydroxide.'Analyti-' cal distillation indicated that a, yield of about 90%N-dimethyl dodecylamine was obtained, B. P. C. at8mm. a

In the reduction of long-chain primary amines according to the processof this invention, it is essential to maintain an excess of the reducingagent in the reaction mixture at all times. With formic acid, theminimum amount required is at least two mols per mol of primary amine,and th reduction is preferably carried out with an excess of. formicacid amounting to at least iive mols per mol of amine. The excessfunctions primarily as a solvent for the reaction andserves to lower.the viscosity of the solution. In.-

the absence of such an xcess, the reaction mixture becomes extremelyviscous, dlflicult to stir, and is likely to go out of control duringthe period of eifervescence owing to the inherent surface activeproperties and tendency to foam of materials in the 12 to 18 carbonrange. In'order to avoid excessive foaming there may be added to thereactants an anti-foaming agent such as ether. As mentioned in the aboveexamples, the use of a solvent or anti-foaming agent does not completelyavoid th danger of product losses through foaming, and extreme care mustbe exercised in adjusting the temperature of the reaction. In mostinstances, the reductio starts at temperatures ranging from roomtemperature to about 35 C., and thenceforth is exothermic untilapproximately 55% to 65% of the theoretical amount of CO2 has beenevolved; This is usually accompanied by a temperature rise to 42 to 45C., and further application by heat is seldom necessary until the dangerof foaming over has passed. Thereafter, raising the temperature of thereaction mixture to the atmospheric pressure boiling point offers butfew difficulties.

The reaction may be carried out under superit is usually preferably andmore convenient to employ commercial formalin solutions containing about37% by weight of formaldehyde. In

conducting the reduction process, the preferred proportions offormaldehyd and primary amine are at least two mols of formaldehyde permol of amine, and it is usually desirable to use approximately 10%excess of formaldehyde.

In a broad sense, this invention contemplates the conversion toN-dimethyl amines of longchain primary amines in which the amino groupis attached to an aliphatic hydrocarbon radical containing at leasttwelve carbon atoms. The hydrocarbon radicals may be straight chain orbranched chain, and the amino group may be attached either to'a terminalcarbon atom or to a secondary or tertiary carbon at some intermediatepoint in the hydrocarbon residue. Typical examples of primary andsecondary amines com? ing within the scope of the invention areoctylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine,octadecylamine, 'I-aminoheptadecane, S-amincdodecane, 8-aminohexadecane,2-methyl-3-aminopentadecane, 8-amino pentadecane, 12-aminooctadecane,dioctylamine, didodecylamine, octyldodecylamine, ditetradecylamine,dihexadecylamine, etc. It will be recognized that, in general, primaryand secondary amines coming within the scope of the invention arethose'containing hydrocarbon radicals which tend to confer surfaceactive properties such as wetting power, detergency and the like on anysolubilized organic derivative containing them. Sodium dodecyl sulfateis, for example, a familiar synthetic detergent.

The process of this invention provides a convenient and practical methodfor the synthesis of valuable long-chain N-methyl or N-dimethyllong-chain tertiary amines. The outstanding advantages of the processare convenience and ease of handling on a commercial scale, high yields,and economy. These characteristics are in marked contrast to methods ofthe prior art referred to above which are known to possess manypractical disadvantages from the standpoint of commercial operation.

The long-chain N -methyl and N-dimethyl amines of the invention arevaluable articles of commerce and may be employed as intermediates forthe preparation of textile reagents, insecticide compositions,moth-proofing agents, and many other materials useful in the arts.

Having described in detail the objectives and preferred embodiments ofmy invention, it is to be understood that I do not limit myself to thespecific disclosures thereof except as defined in the following claims.

I claim:

1. A process for the production of long-chain tertiary amines whichcomprises reducing a mixture of formaldehyde and an amine selected fromthe class consisting of long-chain primary and long-chain secondaryamines with formic acid at a temperature between about 25 C. and about100-Q, said formic acid being present in a molar amount equivalent to atleast twice the amount of amine being treated.

2. A process for the preparation of N-dimethyl long-chain alkyl amineswhich comprises treating a mixture of formaldehyde and a. long-chainprimary amine having from 12 to 18 carbon atoms in the chain with formicacid ata temperature between about 25 C. and about 100 C.

3. A process for the preparation of N-dimethyl long-chain alkyl amineswhich comprises bringing into admixture a primary amine having between12 and 18 carbon atoms and formic acid in molecular excess of at least 5times that of said amine under such condition; that the temperature ofthe mixture does not exceed 60 C., cooling said mixture to roomtemperature and adding formaldehyde, then gradually increasing thetemperature of the mixture until the evolution of carbon dioxide iscomplete, and recovering an N-dimethyl alkyl amine from the reactionproduct. 4. The process in accordance with claim 1 characterized in thatthe formaldehyde is present in a molar amount equivalent to at leasttwice the amount of amine beingtreated.

5. A process for the preparation of N-dimethyl long-chain alkyl amineswhich comprises treating a mixture of formaldehyde and a long-chainprimary amine having from 12 to 18 carbon atoms in the chain with formicacid at a temperature between about 25 C. and about 100 C., said formicacid being present in a molar amount equivalent to at least twice theamount of amine being treated.

6. The process in accordance with claim 5 characterized in that theformaldehyde is present in a molar amount equivalent to at least twicethe amount of amine being treated.

JAMES E. KIRBY.

